Science

Spiders Tune In To Web's Music To Size Up Meals And Mates

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Hairlike sensors on the the legs of the golden silk spider help it "listen" to the thrum of its web.

Some of the toughest stuff in nature is spider silk — as strong, ounce for ounce, as nylon. And a silk web makes a great trap for prey, as well as a nice place for a spider to live.

But scientists have learned that spiders can do something else quite extraordinary with their webs: They can "tune" them, like musical instruments.

This revelation comes from a scientific team in England called the Oxford Silk Group. No, membership isn't about school neckties or silk undergarments. The group studies silk from animals, such as spiders. Why?

"Spider silk has been evolving for over 350 million years," says Beth Mortimer, a lecturer in biology at Oxford University, "and it's something we haven't been able to re-create."

Mortimer and her colleagues recently discovered that many of the silk elements or strands in a web actually vibrate like strings on a musical instrument. "If you think of something like a violin or a guitar," Mortimer says, "for a certain length of string you can have different pitches that come out of your instrument."

A guitar or violin string's thickness, length and tension determine the pitch of the sound it produces when plucked. It turns out spiders know this (even without the benefit of much of a brain), mostly thanks to sensors in their legs. And spiders (at least the golden orb weavers the Silk Group studied) can distinguish between different vibrations or pitches traveling up and down the silk web.

But here's something more amazing: A spider will sometimes tighten or loosen those silk strands to alter the way each string resonates. "It can actually very finely tune how the silks are vibrating," Mortimer says. Her team used lasers to detect the tiniest vibrations in the web — and observed spiders doing this sort of tuning. The scientists describe their work in the current issue of the journal Material Views.

So, OK, these spiders "tune" their webs. But why?

The Silk Group says the array of vibrations coursing through the web provides a kind of information. The spider "reads" these vibrations to, for example, locate where a struggling insect has been snagged. And apparently the web has to be tuned just right to provide that kind of arachnidian triangulation.

And sometimes the spider will even "play" the web to create vibrations and interpret the results. "The spider can actually pluck or bounce the silk strings," says Mortimer, "and it can monitor the echoes that come back so it can locate objects."

Now, with all those strands in a web, you can imagine what the spider must be sensing when a big bug flies into it and thrashes around — a real cacophony.

Sometimes spiders get visitors in their webs that are not prey, though — they're potential mates. Mortimer suspects the web owner can also distinguish that kind of signal from others. She doesn't know what that particular vibrational pattern would feel like to spiders — one can only assume they're pickin' up good vibrations.